An X-ray tube comprises a cathode which emits electrons and an anode target which irradiates X-rays by collision of the emitted electrons, in a vacuum envelope in a vacuum atmosphere. The cathode comprises an electron emission source and a cathode cup which accommodates the electron emission source. The electron emission source is composed of a filament which emits electrons and a support terminal which supports the filament. The filament is provided to be electrically insulated from the cathode cup. The filament is joined to the support terminal by welding or the like.
The filament is heated by heat generated by a flowing current and emits electrons (thermoelectrons) to the anode target. The filament is repeatedly heated in accordance with emission of the electrons and strength of the joint between the filament and the support terminal is thereby reduced. The filament may be therefore displaced from the joint of the support terminal. A focal position of the electrons on the anode target may be displaced by displacement of the filament. In addition, the filament may be brought into contact with the cathode cup (filament touch). If the filament is brought into contact with the cathode cup, a current may not flow to the filament.
The embodiments have been accomplished in consideration of this point and aim to provide an X-ray tube and an X-ray tube manufacturing method that can prevent displacement of the filament of the cathode.